What was the main effect of poll taxes and literacy test put in place in the south at the end of the 19th century

The poll tax and the literacy test were only two of various ways to prevent blacks from voting. The literacy test had the biggest effect, due to Black not knowing how to read in general. What they would do is give a written paper in front of the voter, then say "read this" or "read this in German" or any other language of that.